1. Technical Field
This invention relates to a method of whole-blood collection and the preparation of components therefrom following collection.
2. Background Art
In the conventional method of whole blood collection, a needle is placed in a vein in the donor""s arm and whole blood flows by gravity into a bag which holds a quantity of anticoagulant solution, which prevents the blood from clotting. When a unit of whole blood, defined in the United States as 450 milliliters (ml), has been collected, the needle is removed from the vein and the blood bag is set aside for later transfer to the processing laboratory of the blood center.
It should be noted that the ratio of anticoagulant to whole blood is approximately one to seven; thus the amount of anticoagulant in the bag is 63 ml. It should also be noted that, while the ratio of anticoagulant to whole blood is one to seven after a full unit has been collected, the ratio of anticoagulant to whole blood is considerably higher than one to seven at the beginning of the collection. The red cells flowing into the collection bag at the beginning of the collection are, therefore, subject to xe2x80x9canticoagulant shockxe2x80x9d, which has the effect of damaging some of the red cells. As the collection proceeds, the ratio decreases.
In the processing laboratory, a technician places the bags of whole blood into a large, swinging bucket centrifuge, which must be carefully balanced as the bags are loaded. The centrifuge is started and the bags are spun at a high rate of speed. In the first centrifugation, the red cells, which are the heaviest component, are forced to the bottom of the bag while the platelet-rich plasma, which is lighter, rises to the top. When the bags are removed from the centrifuge, they must be handled carefully so as to avoid remixing.
The technician next places each bag in an xe2x80x9cexpressorxe2x80x9d consisting of two rigid plates that are joined by a spring loaded hinge. One of the plates is fixed and the other is moveable. The blood bag is positioned between the two plates and the spring catch released causing the moveable plate to press against the bag. A port on the top of the bag is then opened and the platelet-rich plasma is expressed into an attached, empty bag. When the technician observes that red cells are about to reach the outlet port, the expression is stopped and the tubing clamped.
If platelets are to be separated, the bags containing the platelet rich plasma are returned to the centrifuge, the load is again balanced and a second spin begins, this time at a higher speed This spin forces the platelets to the bottom of the bag and allows the lighter plasma to rise to the top. The expression process described above is then repeated so that the platelets can be diverted to a separate bag for storage. There are other variations of these blood-component collection and separation processes, including a process for collecting a buffy coat from the blood; all of the variations use centrifugation techniques similar to those described above. Although various devices have been developed and marketed whose function is to minimize the amount of labor required in the expression of components from one bag to another, these devices do not eliminate the centrifugation step described above. Furthermore, these devices are designed to be used in the component-preparation laboratory of the blood center and not at the point of whole blood collection.
It will be appreciated, therefore, that the conventional method of centrifuging and separating components from whole blood is a labor-intensive, manual process. In addition, in order to be convenient to volunteer donors, the majority of whole blood collections take place, not in the blood center, but in mobile units that travel to other locations, such as community centers, offices and factories. Because the bags of whole blood must then be transported back to the blood center for processing and because of the need to schedule the time of laboratory personnel, many hours can elapse between the completion of the collection and the time that component separation begins.
It should be noted that, if the plasma separated from the whole blood is to be used for the production of Factor VIII for transfusion to hemophiliacs, regulations require that the plasma separation must be completed and the plasma frozen within six hours of the time of the whole-blood collection. It can be demonstrated that, the sooner the plasma is frozen, the higher will be the recovery of Factor VIII. It should be further noted that, if the plasma is to be used for transfusion as Fresh Frozen Plasma, regulations require that the separated plasma be placed at xe2x88x9218xc2x0 C. or lower within eight hours of collection from the donor. The practical consequence of these regulations is that blood banks must schedule the times of donations with the times at which laboratory personnel are available to prepare the components.
In addition to the conventional method of whole blood collection and component separation just described, individual blood components can be collected by a process called apheresis. In this process, the donor is connected to a cell separator, a needle is inserted in the donor""s arm, an anticoagulant is added to the whole blood as it is drawn from the donor, and the anticoagulated whole blood is pumped into the rotor of the cell separator where centrifugal force causes the components to separate. The component that is to be retained is directed to a collection bag and the unwanted components are returned to the donor. This process of drawing and returning continues until the quantity of the desired component has been collected, at which point the process is stopped. Apheresis systems are used widely for the collection of single-donor platelets and single-donor plasma. A central feature of these apheresis devices, however, is that, while they separate blood components at the point of collection, they require that the unwanted components must be returned to the donor. This, in turn, means that apheresis devices must incorporate a variety of safety features, such as air detectors and pressure monitors, to protect the donor from harm while the donor is connected to the cell separator. Such safety mechanisms add cost and complexity to apheresis system equipment and disposables.
In contrast to apheresis systems, conventional whole blood collection systems do not return anything to the donor but, on the other hand, neither are they able to separate blood components at the site of collection. There is a need, therefore, for an improved method of whole blood collection and the preparation of components therefrom, without the complexity and expense of conventional apheresis devices, and without the labor-intensive, manual separation process described above.
The present invention provides a system for collecting and processing blood from a donor, wherein the system may be compact enough to be located entirely beside the donor""s chair, and be able to process the blood while the donor is still resting in the chair after having donated the blood. Thus, the separated blood components (plasma and red blood cells) may be stored in their individual optimum environments immediately after the whole blood is drawn, and the blood does not need to be transported back to a separation laboratory for processing.
The system includes a needle (or other cannula-like device) for insertion into a vein of the donor and drawing whole blood therethrough, a variable-volume rotor for holding the blood after it is drawn, and means for spinning the rotor so as to cause the blood to separate into components, for example, plasma and red blood cells. The system also provides for a container for collecting a separated component. In a preferred embodiment two containers are used: the first container for containing an anticoagulant, which is preferably added to the whole blood as it is drawn from the donor, and then for storing the plasma after it has been separated from the red blood cells, and the second container for storing the separated red blood cells. The system further includes tubing, which may have valving built into it and which may be acted on externally, so as to direct the blood components in the desired manner. The tubing connects the needle, the rotor, and the first and second containers. With the valving, the tubing is able to permit (i) the flow of whole blood from the needle to the rotor, (ii) the flow of anticoagulant from the first container to the whole blood flowing from the needle to the rotor, (iii) the flow of plasma from the rotor to the first container, and (iv) the flow of red blood cells from the rotor to the second container. The spinning means and the valving are preferably controlled by an electronic controller. Preferably, the system also includes pumping means, which is also controlled by the controller, and which forces the blood components out of the rotor to the tubing. The pumping means preferably includes means for drawing the whole blood into the rotor.
The system preferably includes an interlock device, connected to the controller, which does not permit the pumping (or flowing) of any blood components from the rotor until the needle has been inserted into the interlock device. This feature ensures that the donor is not still connected to the system when the system is generating pressure for forcing blood components out of the rotor. Preferably, the controller does not permit the rotor to be spun until the needle has been inserted into the interlock device.
In a preferred embodiment, the tubing has a valve, which is connected to three components: to the rotor by a common tube, to the second container by a second-container tube, and to the first container by a first-container tube. The tubing connecting the first container to the rotor is preferably in fluid communication with the needle, so that whole blood can preferably flow through the first-container tube through the valve to the rotor. In this embodiment, the controller includes means for detecting the presence of red blood cells passing from the rotor to the valve means, and causes the valve means to direct the red blood cells to the second container upon the detection of the red blood cells. In one embodiment, the needle is attached to the first-container tube.
In an alternative, preferred embodiment, the needle is connected to the valve means by a separate tube, so that the valve means is connected to four components: the rotor, the first and second containers, and the needle. In this embodiment, the valve means, in one mode, permits flow from the needle to the rotor while allowing anticoagulant to enter this flow at the valve means. In a second mode, the valve means permits no flow from the rotor. In a third mode, the valve means permits flow from the rotor to the first container, and in a fourth mode, the valve means permits flow from the rotor to the second container.
The variable-volume rotor is preferably of the type described in co-pending application Ser. No. 08/322,601, now U.S. Pat. No. 5,733,253, for a xe2x80x9cBlood Processing Systemxe2x80x9d by Headley and Powers, filed Oct. 13, 1994. This application is incorporated herein by reference. In a preferred embodiment of the invention, the rotor includes an elastic diaphragm and a rigid member, which together define a chamber of varying volume (as described in application Ser. No. 08/322,601). The pumping means in this embodiment may apply gas pressure against this diaphragm to force blood components out of the rotor, preferably through the common tube through the valve to their respective containers. The pumping means also preferably includes means for applying a negative gas pressure against the rotor""s diaphragm in order to draw whole blood into the rotor""s chamber.
In a preferred procedure, the system is connected to the donor for collecting the whole blood from the donor, then the system is disconnected from the donor and used to separate the blood into its components by centrifugation. Preferably, the system first draws whole blood through the needle and meters anticoagulant from the first container into the whole blood as it enters the variable-volume rotor. The anticoagulated whole blood then enters the rotor. When the system detects that the desired quantity of whole blood has entered the rotor, the needle is withdrawn from the donor""s arm, following which the rotor is spun so as to separate the whole blood into plasma and red blood cells. After the blood components are separated, the rotor continues to spin to maintain the blood components in their separated state (preferably at a slower rate than that required to achieve the separation), and the plasma is forced out of the rotor and directed to the first container, which held the anticoagulant. Preferably, as noted above, the system is designed so that this forcing the plasma out of the rotor cannot take place until the needle is removed from the donor and inserted into an interlock device After all the plasma has been forced out of the rotor, the red blood cells are forced out and directed to the second container.
In an alternative embodiment of the process, the red blood cells are washed before being dispensed from the rotor. Wash solution is added to the rotor after the plasma has been directed from the rotor but before the red blood cells have been directed from the rotor. The rotor is then agitated so as to mix the wash solution and the red blood cells. After the wash solution and the red blood cells have been mixed, the rotor is spun again so as to separate the wash solution and the red blood cells. The separated wash solution is dispensed from the rotor, and then finally the washed, separated red blood cells are dispensed from the rotor.